液体流变学测量与举例.pptVIP

液体流变学特性测量 与应用举例 流变学测试的作用 通过流变测试，可以： 预测材料特性 解决加工和使用过程中的问题 配方设计 质量控制 产品优化 测量食品的屈服应力 问题: 太低的屈服应力造成制品太稀，易流动 太高的屈服应力使之从容器中取出较困难 重要参数 - 屈服应力 两种调味酱的比较 实验模式: 应力扫描 结果: 样品A屈服应力较高，需要比较剧烈的摇动才能从瓶中取出。 屈服应力影响食品性能或感官知觉的其它例子 蛋糕上的奶油 巧克力 奶油 布丁/奶油蛋羹 Pie 的陷料 Determination Methods Tube Viscometry Three basic categories: 1. Glass capillary viscometer(U-tube viscometer) 2. High pressure capillary viscometer 3. Pipe viscometer Rotational viscometry 1. Concentric cylinder viscometer 2. Cone and plate viscometer 3. Parallel plate viscometer Determination Methods Glass Capillary Viscometer Glass Capillary Viscometer High Pressure Capillary Viscometer Pipe Viscometer Determining Principle Hagen-Poiseulille law Qt/t= (πΔPR4)/(8ηL) η= (tπΔPR4)/(8Qt L ) Qt : flow capacity; ΔP: pressure drop R : radius of capillary pipe L : length of capillary pipe Glass Capillary Viscometer Often used for the determination of relative viscosity of fluid η/ η 0={ (tπΔPR4)/(8Qt L )}/{(t0πΔP0R4)/(8Qt L )} η/ η 0= ΔPt/ ΔP0t0 = ρt/ ρ0t0 η 0 : viscosity of standard fluid ρ0: density of standard fluid Glass Capillary Viscometer Three categories: Constant velocity capillary viscometer Constant pressure capillary viscometer Position-different capillary viscometer This kind of viscometer is more commonly used for the viscosity determination for fluid with less viscous Position-different Capillary Viscometer Two common used capillary viscometer: Ostwald viscometer Ubbelodhe viscometer The difference of the two types of viscometers Determination procedure Example for Capillary Viscometer Viscosity determination using capillary viscometer, Method as follows:1. Making the concentration of P~WSPI1、P~WSPII2、P~AEPNa I1、P~AEPNa I4、P~AEPCa :5mg/ml, 2. Mixing in order to dissolve different pentosan samples, 3. Sucking15ml solutions into Ubbelodhe viscometer ，4. Determining th